I don't know if you can call it shadowing or not, but many times when I'm trolling crankbaits I'll record a route with my trolling motor so I can go back and forth on it. There will be places on that route where I catch fish more often. It's not unusual for me to get to the end of the route and turn around to go back through and there will be boats setting on places where I caught fish. Of course they probably thought I had left when I trolled on by. I usually just go around them and get back on my route.